1. Field of the Invention
The present invention relates to an alternating current motor of the type comprising a combination of magnetic frequency multiplier for increasing frequency of electric current supplied from power supply line and rotor normally usable for induction motor.
2. Description of the Prior Art
To rotate a rotor of the hitherto known alternating current motor at a higher rotational speed there was already made a proposal for energizing the motor with high frequency voltage and thereby rotating the rotor at a higher rotational speed. In the conventional motor of the above-mentioned type a magnetic frequency multiplier was mostly used for increasing the working frequency. Alternatively, an inverter may be employed for the same purpose of increasing the working frequency of supplied electric current.
However, it has been pointed out as drawbacks inherent to the conventional alternating current motor that there is necessity for specific power supply system adapted to change working frequency as required in spite of the advantageous feature that rotational speed can be smoothly controlled with the minimized loss and moreover installation of the conventional motor is carried out at a very expensive cost.
Further, there was made another proposal for utilizing a frequency converter with a circuit including semiconductors incorporated therein. Practically, it has been found that this proposal has an advantageous feature that rotational speed of the motor can be adjusted as required by changing the working frequency of supplied electric current but when shifting the direction of transmission of electric current, there is generated noisy sound and in some place an occurrence of electric wave hindrance is unavoidably recognized.